Ambient condition detectors have been found to be useful in providing an indication of the presence of the respective condition. Smoke detectors have been found useful in providing early warnings of the presence of airborne particulate matter such as smoke.
Known smoke detectors often include a housing with an internal smoke chamber. Either an ionization-type or a photoelectric-type smoke sensor can be located in the housing.
Vents are located in the housing. Ambient air circulates into and out of the housing in response to movement of the adjacent atmosphere.
Air circulation in a region being monitored does bring the airborne particulate matter into the housing. Depending on the nature of the air currents, this can be faster or a slower process.
In large commercial buildings air circulation is often achieved by centralized heating and cooling systems. Building control systems alter air flow in response to preset schedules. Hence, there may be time of minimal or no circulation such as evenings or weekends. There continues to be a need for solutions to these minimal or no circulation situations. Therefore the present invention provides                a) a smoke, CO, CO2 or N sensing chamber having a hollow housing having first and second regions separated by at least one flow opening, the first region, except for the at least one flow opening, does not have any outflow ports and has at least one atmospheric inflow port; and the second region, except for the at least one flow opening, does not have any inflow ports and has at least one outflow port; and a non-movable flow inducing element carried in at least one of the first or second regions of the housing to create a temperature gradient therein;        b) a detector having an aspirated sensing chamber that includes first and second regions separated by at least one flow opening and a temperature gradient between the first and second regions is the sole cause of atmospheric flow into, between and out of the chamber, the temperature gradient being provided by a non-movable flow inducing atmospheric heating element in at least one of the first or second regions of the sensing chamber; and        c) a method that establishes a chamber for sensing an airborne ambient condition which includes the steps of:separating the chamber into first and second regions by at least one flow opening;establishing flow between the first and second regions and into the chamber wherein the flow is created solely by establishing a temperature gradient between the first and second regions of the chamber to induce an inflow of ambient atmosphere into the chamber; and sensing a concentration of the ambient condition in the chamber.        